Multistage centrifugal compressors are used for a variety of applications requiring high pressure, high volume throughput of a particular gas. To a large extent, such compressors are custom sized and manufactured to meet customer's specifications with tolerances and configurations being closely held on the various components in order to assure the design performance intended for the equipment. Such compressors are constructed from a plurality of parts forming the diffusers. The parts are positioned in end to end relationship forming the compressor.
Despite the accuracy of manufacture, a problem has been identified as associated with relatively small diffuser widths of such compressors in, for example, the last stage of a barrel-type straight through compressor or a back-to-back type compressor. Specifically, it has been found that in such compressors, the overall length of the multiplicity of parts sometimes rsults in at least one wall of the last diffuser stage tends to move slightly because of resultant stresses imposed by high operating pressures, causing width enlargement beyond the design dimensions. The resultant increase in diffuser flow width can typically amount to on the order of about 0.03 inches (0.76 cm) at differential pressures of 30 psig (207 KPa) in a compressor with a casing diameter of 60 inches (150 cm) or on the order of about 0.04 inches (0.102 cm) at differential pressures of 300 psig (2070 KPa) in a 24 inch (60 cm) casing diameter.
Such width changes in the diffuser are, of course undesirable in that it tends to alter the design performance of the compressor at the affected stage. Notwithstanding recognition of the problem, however, a solution therefor has not heretofore been known.